Growing Shiitake Mushroom June 16 2014

Description

Cap 5-25 cm broad, hemispheric, expanding to convex and eventually plane at matu­rity. Cap dark brown to nearly black at first, becoming lighter brown in age, or upon drying. Cap margin even to irregular inrolled at first, then incurved, flattening with maturity and often undulating with age. Gills white, even at first, becoming serrated or irregular with age*, white, bruising brown when damaged. Stem fibrous, centrally to eccentrically attached, fibrous, and tough in texture. Flesh bruises brownish.

Distribution

Limited to the Far East, native to Japan, Korea, and China. Until recently, not known from North America. Two sitings of wild Shiitake have been confirmed from Washington and California (Ammirati, 1997; Desjardin, 1998). These naturalized races have apparently escaped from cultivated Shiitakes and are adapting. Considering the continued deforestation of the Far East, where the genome of this mushroom appears increasingly endangered, these sitings may serve to protect the Shiitake genome.

Natural Habitat

This mushroom grows naturally on dead or dying broadleaf trees, particularly the Shii tree (Castanopsis cuspidata), Pasania spp., Quercus spp., and other Asian oaks and beeches. Although occasionally found on dying trees, Shiitake is a true saprophyte exploiting only necrotic tissue.

Mycelial CharacteristicsMushroom mycelium white at first, becoming longitudinally linear and cottony-aerial in age, rarely, if ever truly rhizomorphic. In age, or in response to damage, the mycelium becomes dark brown. Some strains develop hyphal aggregates—soft, cottony ball-like structures—that may or may not develop into primordia. Many mycologists classify this species as a white rot fungus for the appearance of the wood after colonization. However; the mycelium of Shiitake is initially white, soon becoming chocolate brown with maturity, leaving a white-pulped wood.

Fragrance SignatureGrain spawn has a smell similar to crushed fresh Shiitake, sometimes slightly astringent and musty. Sawdust spawn has a sweeter, fresh, and pleasing odor.

Natural Method of CultivationOn hardwood logs, especially oak, sweetgum, poplar; cottonwood, eucalyptus, alder; ironwood, beech, birch, willow, and many other non-aromatic, broadleaf woods. The denser hardwoods produce for as long as 6 years. The more rapidly decomposing hardwoods have approximately half the life span, or about 3 years. The fruitwoods are notoriously poor for growing Shiitake. Although Shiitake naturally occurs on oaks and beeches, the purposeful cultivation of this mushroom on hardwood stumps in North America has had poor success thus far.

For information on the cultivation of Shiitake on logs, see Kruger (1992), Fujimoto (1989), Przybylowicz and Donoghue (1988), Leatham (1982), Komatsu (1980, 1982), Kuo and Kuo (1983), and Harris (1986). Several studies on the economics of log cultivation have been published to date. Kerrigan (1982) published a short booklet on the economics of Shiitake cultivation on logs, which sought to show the profitability of Shiitake log culture. Gormanson and Baughman (1987) published an extensive study and concluded that profitability of growing Shiitake outdoors, as in Japan, was marginal at best. Roberts (1988) reviewed their statistical models and concluded that Shiitake cultivation on logs was not profitable. In the most recent study on log Shiitake industry in the United States, Rathke and Baughman (1993) concluded that when a production threshold of4,000 logs/year was achieved by an experienced grower the net profit on money invested, after costs, was a mere 5.76% return after-tax equivalent. Increasing production to 8,000 logs had no appreciable increase in profitability. Joe Deden, who once was the mushroom project manager at the Forest Resource Center outside of Lanesboro, Minnesota, has been instrumental in matching Shiitake strains with various woods, and bringing Shiitake log cultivation to the forefront of public awareness.

Recommended Containers for FruitingPolypropylene, high-density, thermotolerant polyethylene bags, usually fitted with a microporous filter patch, or stuffed with a cotton plug. Bottle fruitings are impractical. Tray fruitings a la Button mushroom culture have been employed with some success in Europe. However; the advantage of bag culture is that contaminants can be isolated, limiting cross-contamination of adjoining substrates.

Yield Potentials1.5-3 pounds of fresh mushrooms from 6 pounds of sawdust/chip/bran. Biological efficiency rating of 100-200% using the methods described herein.

Harvest Hints

Humidity should be constantly fluctuated during fruitbody development and then lowered to 60% RH for 6 to 12 hours before the crop is harvested. This causes the cap's leathery, outer skin to toughen, substantially extending shelf life. Most people prefer to pick the mushrooms when the margins are still inrolled, at a mid-adolescent stage. However; greater yields are realized if the fruitbodies are allowed to enlarge. For best results, the growing room manager must carefully balance the interests of quality vs. yield throughout the cropping process.

Although these mushrooms can withstand a more forceful water spray than Oyster and other mushrooms, Shiitake gills readily bruise brownish, reducing quality. (Outdoor-grown Shiitake commonly has brown spots caused by insects. These damaged zones later become sites for bacterial blotch.) Mushrooms should be trimmed flush from the surface of the blocks with a sharp knife so no stem butts remain. Dead stems are sites for mold and attract insects. Thumbs should be wrapped with tape, or protected in some manner, as the pressure needed to cut through Shiitake stems is substantially greater than that of most fleshy mushrooms.

Form of Product Sold to MarketFresh mushrooms, dried, powdered, and extracts. In Japan Shiitake wine, Shiitake cookies, and even Shiitake candies are marketed.